1. Technical Field
Exemplary aspects of the present disclosure generally relate to a belt tracking system, a roller assembly, and an image forming apparatus employing the same, and more particularly, to a belt tracking system for adjusting misalignment of a movable belt in an axial direction of a plurality of rollers about which the movable belt is entrained, a roller assembly, and an image forming apparatus employing the belt tracking system.
2. Description of the Related Art
Known image forming apparatuses employ various types of movable belts, such as an intermediate transfer belt, a media conveyor belt, and a fixing belt, each of which is entrained about a plurality of generally parallel support rollers and rotated by the rotation of the rollers. Due to wear and tear of parts used to rotate the belt support rollers, the belt support rollers are no longer aligned parallel to each other. Furthermore, because multiple parts are connected, the parts vary from one to another and variation among these parts can cause a different degree of connection at the left end and the right end of the rollers. As a result, the support rollers are not aligned parallel.
When these rollers are no longer parallel, the belt runs over the rollers in the axial direction of the rollers, resulting in breakage of the belt.
To address this difficulty, several techniques have been proposed which employ a belt tracking system to correct the position of the belt which has drifted in the axial direction of the roller. For example, there is known a belt tracking system in which a rotary member with an inclined surface and a stationary guide member are provided to correct displacement of the belt. Such a configuration is proposed in JP-2009-288426-A.
In order to facilitate an understanding of the related art and of the novel features of the present invention, with reference to FIGS. 11A through 11D, a description is provided of the known belt tracking system to correct displacement of the belt proposed in JP-2009-288426-A.
As illustrated in FIG. 11A, the belt tracking system includes a roller 910 about which a sheet conveyor belt 900 is entrained, rotary members 920a and 920b including inclined surfaces 930a and 930b, respectively, and stationary guide members 940a and 940b that contact the inclined surfaces 930a and 930b, respectively. FIG. 11A illustrates the sheet conveyor belt 900 without skew. As illustrated in FIG. 11A, when the sheet conveyor belt 900 is in its proper operational position without skew, the rotary members 920a and 920b at each end of the roller 910 in the axial direction thereof contact the stationary guide members 940a and 940b, respectively.
By contrast, as illustrated in FIG. 11B, when the sheet conveyor belt 900 drifts to one side, the belt edge contacts and presses against one of the rotary members 920a and 920b in the axial direction, causing the pressed rotary member 920a (or 920b) to move in the direction of skew of the belt 900 (in this example, the rotary member 920a is pressed to the right side of the drawing). As a result, as illustrated in FIG. 11B, the inclined surface 930a of the rotary member 920a at one axial end of the roller 910 contacts the stationary guide member 940, causing the roller 910 at that axial end to tilt downward. The end of the roller 910 at the rotary member 920a side tilts downward, thereby moving the sheet conveyor belt 900 in a direction opposite the direction of skew and hence correcting the position of the sheet conveyor belt 900.
Although generally advantageous, when the roller 910 in the state shown in FIG. 11B moves toward the rotary member 920a, the other rotary member, i.e., the rotary member 920b moves in the same direction. At this time, the inclined surface 930b of the rotary member 920b at the opposed end of the rotary member 920a separates from the stationary guide member 940b such as shown in FIG. 11C, hindering proper rotation of the roller 910.
If the sheet conveyor belt 900 moves to the rotary member 920b as illustrated in FIG. 11D after the inclined surface 930b of the rotary member 920b separates from the stationary guide member 940b, the end of the roller 910 at the rotary member 920b side needs to tilt downward in order to correct the position of the sheet conveyor belt 900.
However, since the inclined surface 930b is not in contact with the stationary guide member 940b, the end of the roller 910 at the rotary member 920b side cannot tilt downward, thereby complicating efforts to correct the position of the sheet conveyor belt 900.